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United States Patent | 5,258,698 |
Piovano ,   et al. | November 2, 1993 |
The device is provided on a machine tool, wherein the drilling or milling operating head (12) comprises an axially movable spindle (14) and a workpiece hold-down (17), and wherein the working depth is controlled according to the relative position of the tool (16) with respect to the hold-down (17), defined by sensing a reference member (56) by means of the tool (16). To avoid the errors due to the thermal expansion in defining the reference position between the tool and the hold-down, before the reference member (56) is sensed, an electric power supply heats the spindle (14) by sequentially energizing the phases of the statoric coil of the spindle electric motor (76). The reference member (56) comprises a proximity sensor (64) operated by the tool (16) through an air pad piston (67).
Inventors: | Piovano; Luigi (S. Giusto Canavese, IT); Gaida; Guido (Ponderano, IT); Franciscono; Giuseppe (Alice Castello, IT); Ottone; Renato (Cascinette d'Ivrea, IT) |
Assignee: | Pluritec Italia S.p.A. (Burolo, IT) |
Appl. No.: | 727568 |
Filed: | July 9, 1991 |
Aug 07, 1990[IT] | 67620 |
Current U.S. Class: | 318/569; 219/121.7; 318/573; 408/35; 483/11 |
Intern'l Class: | H02P 005/40; B23B 039/08 |
Field of Search: | 318/560-574 364/474.10-474.29 219/69.12,69.1,69.15,69.17 408/35 29/38 R 82/129,159 204/224 M,129.35 |
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4669927 | Jun., 1987 | Zeller | 408/13. |
4765784 | Aug., 1988 | Karwan | 408/10. |
4813122 | Mar., 1989 | Watanabe et al. | 408/35. |
4835838 | Jun., 1989 | Hirose | 29/568. |
4865494 | Sep., 1989 | Gudow | 408/13. |
4887493 | Dec., 1989 | Drake | 29/800. |
5010232 | Apr., 1991 | Arai et al. | 219/121. |
5131481 | Jul., 1992 | Smith | 175/428. |
Foreign Patent Documents | |||
2038157 | May., 1972 | DE. | |
3719167 | Nov., 1988 | DE. |
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